Field of the Invention
This invention relates to measuring coatings or films on substrates. More particularly, this invention relates to measuring boron carbide coatings on thin metallic foils.
Description of the Related Art
A number of different techniques are in use to measure thin film thickness including optical or x-ray interferometry, surface profilometry, scanning probe microscopy, cross section electron microscopy and others. Each of these techniques has their own advantages and disadvantages. For example optical or x-ray interferometry can be used to measure wide range of thicknesses ranging from nanometers to several micrometer but requires extremely smooth and flat film-substrate interface. This technique becomes unusable when it comes to a substrate having flexible or rough surface or both. Surface profilometry requires a sharp step height and rigid sample surface. Scanning probe microscopy can measure just few nanometers height and requires a sharp step height and smooth surface. One of the techniques very widely used is the electron microscopy including both scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM can be used to measure in a wide range from tens of nanometers to millimeters and TEM can be used to accurately measure thickness in nanometer scale. However, both of these techniques are very local and require huge effort in sample preparation and can take several hours to measure one sample. It becomes even more difficult when it comes to non-conducting ceramic films since an additional conducting coating is required. Sample preparation becomes even more tedious when the substrate is flexible. Since the techniques are very local measured value will have very high uncertainty for films with rough surface.
Boron-coated straw detector technology was first patented by Dr. Lacy in U.S. Pat. No. 7,002,159 entitled “Boron-Coated Straw Neutron Detector” based upon a Nov. 13, 2002, filing. As the thought leader of this technology area, Dr. Lacy continued his research and development to improve the boron coated straw detectors technology and to find new uses. Examples of Dr. Lacy's continued progress in this technology area are found in his other issued patents and pending patent applications which include: U.S. Pat. No. 8,330,116 entitled “Long Range Neutron-Gamma Point Source Detection and imaging Using Rotating Detector”; U.S. Pat. No. 8,569,710 entitled “Optimized Detection of Fission Neutrons Using Boron-Coated Straw Detectors Distributed in Moderator Material”; U.S. Pat. No. 8,907,293, entitled “Optimized Detection of Fission Neutrons Using Boron-Coated Straw Detectors Distributed in Moderator Material”; U.S. patent application Ser. No. 13/106,785 filed May 12, 2011, entitled “Sealed Boron-Coated Straw Detectors” (allowed and issue fee paid); U.S. patent application Ser. No. 13/106,818 filed May 12, 2011, entitled “Neutron Detectors for Active Interrogation” (allowed and issue fee paid); U.S. Pat. No. 8,941,075, entitled “Boron Coated Straw Detectors with Shaped Straws”; U.S. application Ser. No. 14/060,015 filed Oct. 22, 2013, entitled “Method and Apparatus for Coating Thin Foil with a Boron Coating”; and U.S. application Ser. No. 14/060,507 filed Oct. 22, 2013, entitled “Method and Apparatus for Fabrication Boron Coated Straws for Neutron Detectors.” The patent and pending applications mentioned in this paragraph are hereby incorporated by reference in their entirety for all purposes, including but not limited to those portions describing the structure and technical details of the boron-coated straw detectors and boron coating as background and for use as specific embodiments of the present invention, and those portions describing other aspects of manufacturing and testing of boron-coated straws that may relate to the present invention.
Dr. Lacy also widely published articles on boron-coated straw detection capabilities, fabrication, and development of prototypes for various applications including:    J. L. Lacy, et al, “Novel neutron detector for high rate imaging applications”, IEEE Nuclear Science Symposium Conference Record, 2002, vol. 1, pp. 392-396;    J. L. Lacy, et al, “Straw detector for high rate, high resolution neutron imaging”, in IEEE Nuclear Science Symposium Conference Record, 2005, vol. 2, pp. 623-627;    J. L. Lacy, et al, “High sensitivity portable neutron detector for fissile materials detection”, IEEE Nuclear Science Symposium Conference Record, 2005, vol. 2, pp. 1009-1013;    J. L. Lacy, et al, “Performance of 1 Meter Straw Detector for High Rate Neutron Imaging”, IEEE Nuclear Science Symposium Conference Record, 2006, vol. 1, pp. 20-26;    J. L. Lacy, et al, “Long range neutron-gamma point source detection and imaging using unique rotating detector”, IEEE Nuclear Science Symposium Conference Record, 2007, vol. 1, pp. 185-191;    J. L. Lacy, et al, “Fabrication and materials for a long range neutron-gamma monitor using straw detectors”, IEEE Nuclear Science Symposium Conference Record, 2008, pp. 686-691;    J. L. Lacy, et al, “One meter square high rate neutron imaging panel based on boron straws”, IEEE Nuclear Science Symposium Conference Record, 2009, pp. 1117-1121;    J. L. Lacy, et al, “Boron coated straw detectors as a replacement for 3He”, IEEE Nuclear Science Symposium Conference Record, 2009, pp. 119-125;    J. L. Lacy, et al, “One meter square high rate neutron imaging panel based on boron straws”, IEEE 2009 Nuclear Science Symposium Conference Record, 2009, pp. 1117-1121;    J. L. Lacy, et al, “Initial performance of large area neutron imager based on boron coated straws”, IEEE 2010 Nuclear Science Symposium Conference Record, 2010, pp. 1786-1799;    J. L. Lacy, et al, “Initial performance of sealed straw modules for large area neutron science detectors”, IEEE 2011 Nuclear Science Symposium Conference Record, 2011, pp. 431-435;    J. L. Lacy, et al, “Straw-Based Portal Monitor 3He Replacement Detector with Expanded Capability”, IEEE 2011 Nuclear Science Symposium Conference Record, 2011, pp. 431-435;    J. L. Lacy, et al, “Performance of a Straw-Based Portable Neutron Coincidence/Multiplicity Counter”, IEEE 2011 Nuclear Science Symposium Conference Record, 2011, pp. 529-532;    J. L. Lacy, et al, “Replacement of 3He in Constrained-Volume Homeland Security Detectors”, IEEE 2011 Nuclear Science Symposium Conference Record, 2011, pp. 324-325;    J. L. Lacy, et al, “Initial performance of sealed straw modules for large area neutron science detectors”, IEEE 2011 Nuclear Science Symposium Conference Record, 2011, pp. 431-435;    J. L. Lacy, et al, “Boron-coated straws as a replacement for 3He-based neutron detectors”, Nuclear Instruments and Methods in Physics Research, Vol. 652, 2011, pp. 359-363;    J. L. Lacy, et al, “Design and Performance of High-Efficiency Counters Based on Boron-Lined Straw Detectors”, Institute of Nuclear Materials Management Annual Proceedings, 2012;    J. L. Lacy, et al, “Boron-coated straw detectors of backpack monitors”, IEEE Transactions on Nuclear Science, Vol. 60, No. 2, 2013, pp. 1111-1117.    J. L. Lacy, et al, “The Evolution of Neutron Straw Detector Applications in Homeland Security”, IEEE Transactions on Nuclear Science, Vol. 60, No. 2, 2013, pp. 1140-1146.The publications mentioned in this paragraph are hereby incorporated by reference in their entirety for all purposes, including but not limited to those portions describing the structure and technical details of the boron-coated straw detectors and boron coatings as background and for use as specific embodiments of the present invention, and those portions describing other aspects of manufacturing and testing of boron-coated straws that may relate to the present invention.